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Putting together the ingredients:
scenarios on the origin of the diversity of
planetary systems
Alessandro Morbidelli
CNRS...
Radial velocity (Mayor et al., 2011) and
transit surveys (Howard et al., 2012;
Petigura et al., 2013; Fressin et al., 2013...
Giant planet orbital distribution
Our Solar System have giant planets, like probably only ~15-25% of the other stars,
but ...
The great dichotomy of the Solar System
IDEA
r
snowline
Icy particles fluxSilicate particles
flux
D ~ cm-dmD < mm
Assume:
• A mass-flux that decreases by a factor...
IDEA
r
snowline
Icy particles fluxSilicate particles
flux
D ~ cm-dmD < mm
Morbidelli, Lambrechts, Bitsch and Jacobson, Ica...
r
snowline
This should be the generic initial structure of a planetary system as long as:
1. The disk has a constant aspec...
r
snowline
A super-Earth at the inner edge of the disk from the
accumulation of all the pebbles not accreted by the other ...
r
snowline
The Solar System might have
formed a super-Earth at the
inner edge of the disk, which
migrated out and became t...
r
snowline
(Oka et al., ApJ, 738, 2011)
THE SNOWLINE PROBLEM
r
snowline
Morbidelli and Nesvorny, 2012
Lambrechts, Johansen and Morbidelli, 2014
Particles flow:
Planetesimal seeds:
t1:
r3 AU
snow line
r
snow line
3 AU
r
snow line
3 AU
t2: Jupiter at
20 Earth
masses
f...
r
snowline
MIGRATION ISSUES !!
Current migration maps lead to an absurd situation
Bitsch et al., 2015
All our giant planets should have started growing f...
Observed radial distribution of giant planets (more massive than Saturn)
Only few giant planets migrate all the way to the...
How to explain the bulk of gas giants at 1-2 AU? Photoevaporation! Alexander and Pascucci, 2012)
How to explain the bulk of gas giants at 1-2 AU? Photoevaporation! Alexander and Pascucci, 2012)
How to explain the bulk of gas giants at 1-2 AU? Photoevaporation! Alexander and Pascucci, 2012)
Super-Earths, instead, managed to penetrate into the inner disk
before photo-evaporation divided the disk in two
Izidoro e...
We may conceive the following scenario:
r
If the outer disk produces only super-Earth mass objects, they migrate into the ...
r
We may conceive the following scenario:
If the innermost SE manages to grow to a giant planet, its migration is slowed d...
Giant planets are extremely effective in retaining Super-Earths behind them
(Izidoro, Raymond and Morbidelli, ApJ 800L, 22...
Giant planets are extremely effective in retaining Super-Earths behind them
(Izidoro, Raymond and Morbidelli, ApJ 800L, 22...
IMPLICATION FOR EXTRASOLAR SYSTEMS
If close-in SENs originated by inward migration and if it is the innermost SEN that is ...
r
In our Solar System we think that Jupiter and Saturn migrated
outwards due to their combined interactions with the disk
...
The large obliquities of
Uranus and Neptune indicate
that these planets should
have experienced giant
collisions and this ...
The large obliquities of
Uranus and Neptune indicate
that these planets should
have experienced giant
collisions and this ...
Izidoro et al., 2014
This may not have been an accident:
The inward migration of a SE would have prevented the formation o...
Izidoro et al., 2014
This may not have been an accident:
The inward migration of a SE would have prevented the formation o...
Giant planets are the key!
• The formation of big icy planets (SENs) beyond the snowline should be generic…
• …as well as ...
Time
Semimajoraxis
Jupiter
Saturn
Uranus
Neptune
~25 MEarth
~25 MEarth
Fast Migration
~Saturn Mass
Type II
migration start...
The Nice model:
Tsiganis et al., 2005; Gomes et
al., 2005; Morbidelli et al.,
2007; Levison et al., 2011;
Nesvorny and Mor...
The Nice model:
Tsiganis et al., 2005; Gomes et
al., 2005; Morbidelli et al.,
2007; Levison et al., 2011;
Nesvorny and Mor...
Final orbit of
Jupiter if
encounters with
Saturn occur
Final orbit of Jupiter
if Jupiter-Saturn
encounters do not
occur.
P...
If this had happened, we would not be here to talk about it
Raymond et al.
Conclusions
The Three Chances of our Solar System:
1. The innermost core became a giant planet
2. The mass ratio between J...
r
r
r
t0=½ tν
t1>t0
t2>t1
condensation
line
condensation
line
condensation
line
r0
ur
vr
cond
dry gaswet gas
dry gaswet ga...
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Putting together the ingredients - Alessandro Morbidelli

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Brave new worlds
May 29-June 03, 2016 – Lake Como School of Advanced Studies

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Putting together the ingredients - Alessandro Morbidelli

  1. 1. Putting together the ingredients: scenarios on the origin of the diversity of planetary systems Alessandro Morbidelli CNRS/Observatoire de la Cote d'Azur, Nice, France.
  2. 2. Radial velocity (Mayor et al., 2011) and transit surveys (Howard et al., 2012; Petigura et al., 2013; Fressin et al., 2013) suggest that many (most?) solar-type stars have close-in Super-Earths / Neptune-like (SEN) planets The Solar System is atypical in that our Neptune-like planets are not close-in, but they are beyond Jupiter & Saturn Batygin and Laughlin, 2015
  3. 3. Giant planet orbital distribution Our Solar System have giant planets, like probably only ~15-25% of the other stars, but our giant planets have orbits very different from the extrasolar ones discovered so far. We now know that our Solar System is not typical: 65-80% of solar-type stars have planetary systems different from ours ! We don’t know yet from observations if our Solar System represents 10%, 1%, 10-4, 10-6 of the planetary systems We need theory of planet formation/evolution to address this question
  4. 4. The great dichotomy of the Solar System
  5. 5. IDEA r snowline Icy particles fluxSilicate particles flux D ~ cm-dmD < mm Assume: • A mass-flux that decreases by a factor ~2 at the snowline • An order of magnitude change in particle size (this could be due to the disintegration of dirty-icy pebbles into a collection of silicate grains due to ice sublimation (Morbidelli et al., 2015) or to a change of collisional regime (Banzatti et al., 2016)
  6. 6. IDEA r snowline Icy particles fluxSilicate particles flux D ~ cm-dmD < mm Morbidelli, Lambrechts, Bitsch and Jacobson, Icarus (2015) Core beyond the snowline Embryo within the snowline If the small particle layer is thick enough so that their accretion is a 3D process, then smaller particles are more difficult to accrete. From Hp=Hg(α/τ)1/2 this requires α~10-4
  7. 7. r snowline This should be the generic initial structure of a planetary system as long as: 1. The disk has a constant aspect ratio inside of the snowline and is flared beyond it 2. The drag of the particles is in the Epstein regime
  8. 8. r snowline A super-Earth at the inner edge of the disk from the accumulation of all the pebbles not accreted by the other objects (Chatterjee and Tan, 2014, 2015)? Why not in the Solar System?
  9. 9. r snowline The Solar System might have formed a super-Earth at the inner edge of the disk, which migrated out and became the seed for the core of Jupiter: Raymond et al., 2016
  10. 10. r snowline (Oka et al., ApJ, 738, 2011) THE SNOWLINE PROBLEM
  11. 11. r snowline Morbidelli and Nesvorny, 2012 Lambrechts, Johansen and Morbidelli, 2014
  12. 12. Particles flow: Planetesimal seeds: t1: r3 AU snow line r snow line 3 AU r snow line 3 AU t2: Jupiter at 20 Earth masses fossilized snow line ice ice t> t2 silicate silicate
  13. 13. r snowline MIGRATION ISSUES !!
  14. 14. Current migration maps lead to an absurd situation Bitsch et al., 2015 All our giant planets should have started growing far out (>15 AU) What about bodies growing in the 5-15 AU region?
  15. 15. Observed radial distribution of giant planets (more massive than Saturn) Only few giant planets migrate all the way to the star!
  16. 16. How to explain the bulk of gas giants at 1-2 AU? Photoevaporation! Alexander and Pascucci, 2012)
  17. 17. How to explain the bulk of gas giants at 1-2 AU? Photoevaporation! Alexander and Pascucci, 2012)
  18. 18. How to explain the bulk of gas giants at 1-2 AU? Photoevaporation! Alexander and Pascucci, 2012)
  19. 19. Super-Earths, instead, managed to penetrate into the inner disk before photo-evaporation divided the disk in two Izidoro et al., in prep.
  20. 20. We may conceive the following scenario: r If the outer disk produces only super-Earth mass objects, they migrate into the inner disk?
  21. 21. r We may conceive the following scenario: If the innermost SE manages to grow to a giant planet, its migration is slowed down and it retains the other super-Earth(s) behind it
  22. 22. Giant planets are extremely effective in retaining Super-Earths behind them (Izidoro, Raymond and Morbidelli, ApJ 800L, 22I) Izidoro et al., 2015, ApJ 800L, 22I
  23. 23. Giant planets are extremely effective in retaining Super-Earths behind them (Izidoro, Raymond and Morbidelli, ApJ 800L, 22I) Izidoro et al., 2015, ApJ 800L, 22I SEs jumping across the giant planet orbit can happen, but only in 10-20 % of the cases
  24. 24. IMPLICATION FOR EXTRASOLAR SYSTEMS If close-in SENs originated by inward migration and if it is the innermost SEN that is the most likely to become a giant planet then we expect an anti-correlation between close-in SENs and giant planets. Systems of close-in SENs <-> no giant planets A single close-in SEN <-> a giant planet further out No close-in SENs <-> a giant planet further out Of course, we expect this correlation not to be 100% true. Some close-in SENs might have formed in-situ, in other cases the giant planet might not have formed from the innermost SEN. The reliability of this correlation (to be observationally determined) will tell us how often the ifs are valid and therefore it will allow us to infer information on the origin of close-in SENs and formation of giant planets. r r r
  25. 25. r In our Solar System we think that Jupiter and Saturn migrated outwards due to their combined interactions with the disk Uranus and Neptune did not migrate into the inner Solar System because they have been retained by Jupiter and Saturn
  26. 26. The large obliquities of Uranus and Neptune indicate that these planets should have experienced giant collisions and this suggests they assembled from several merging embryos. The dynamical barrier offered by Jupiter and Saturn offers a framework for this to happen Izidoro et al., MNRAS In press Jakubik et al., 2012 ORIGIN OF URANUS AND SATURN Jupiter Saturn
  27. 27. The large obliquities of Uranus and Neptune indicate that these planets should have experienced giant collisions and this suggests they assembled from several merging embryos. The dynamical barrier offered by Jupiter and Saturn offers a framework for this to happen Izidoro et al., MNRAS In press Jakubik et al., 2012 ORIGIN OF URANUS AND SATURN Jupiter Saturn
  28. 28. Izidoro et al., 2014 This may not have been an accident: The inward migration of a SE would have prevented the formation of errestrial planets
  29. 29. Izidoro et al., 2014 This may not have been an accident: The inward migration of a SE would have prevented the formation of errestrial planets
  30. 30. Giant planets are the key! • The formation of big icy planets (SENs) beyond the snowline should be generic… • …as well as their migration into the inner system • If the innermost SEN becomes a gas-giant planet it can offer a dynamical barrier against the migration of the other SENs into the inner disk • The migration of SENs is constrained by the migration of the gas-giant planet • In most extrasolar systems, gas-giant planets migrated down to ~ 1-2 AU • In our system, the mass ratio between Saturn and Jupiter promoted outward migration (distant giant planets). This retained our SENs (Uranus and Neptune) in the outer solar system, thus protecting the “terrestrial planet region”. • This allowed the Earth to form….. • Chemical properties (e.g. water abundance) are also set by the presence of giant planets governing the radial motion of icy particles
  31. 31. Time Semimajoraxis Jupiter Saturn Uranus Neptune ~25 MEarth ~25 MEarth Fast Migration ~Saturn Mass Type II migration starting ~ 200 MEarth Capture in Resonance Gas disk starts to dissipate • The large eccentricities of the extrasolar gas-giant planets are believed to be the consequence of past orbital instability • The Solar System passed through a giant planet instability as well quasi-circular, resonant, compact orbits current, separated, moderately eccentric orbits Gas-disk era
  32. 32. The Nice model: Tsiganis et al., 2005; Gomes et al., 2005; Morbidelli et al., 2007; Levison et al., 2011; Nesvorny and Morbidelli, 2012
  33. 33. The Nice model: Tsiganis et al., 2005; Gomes et al., 2005; Morbidelli et al., 2007; Levison et al., 2011; Nesvorny and Morbidelli, 2012
  34. 34. Final orbit of Jupiter if encounters with Saturn occur Final orbit of Jupiter if Jupiter-Saturn encounters do not occur. Planet instabilities seem to be more the rule than the exception. Extrasolar giant planet eccentricities are explained by instabilities Period-ratio distribution of SEs is also explained by instabilities The key is that the instability in the Solar System was a weak one because our giant planets are relatively low-mass and in addition Jupiter and Saturn, by chance, did not encounter with each other.
  35. 35. If this had happened, we would not be here to talk about it Raymond et al.
  36. 36. Conclusions The Three Chances of our Solar System: 1. The innermost core became a giant planet 2. The mass ratio between Jupiter and Saturn prevented these planets to come too close to 1 AU 3. The giant planet instability was mild because Jupiter and Saturn avoided mutual encounters All this suggests that the Solar System must be very a-typical
  37. 37. r r r t0=½ tν t1>t0 t2>t1 condensation line condensation line condensation line r0 ur vr cond dry gaswet gas dry gaswet gas dry gaswet gas vr cond ur

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